Oil well cementing process and apparatus therefor



c. B. HOLT 3,205,945

OIL WELL CEMENTING PROCESS AND APPARATUS THEREFOR Sept. 14, 1965 C. B.HOLT- INVENTOR.

Filed June 25, 1962 BY a /MW ATTORNEY United States Patent 3,205,945 OILWELL CEMENTKNG PROCESS AND APPARATUS THEREFOR Clarence B. Holt, Borger,Tex.; D. E. Holt, J12, and Mildred Jewel Holt, executors of saidClarence B. Holt, deceased, assignors to Holt Specialty Company, Pampa,

Tex.

Filed June 25, 1962, Ser. No. 204,896 7 Claims. (Cl. 166-23) Thisinvention relates to an oil well cementing process and apparatustherefor. In the normal procedure of cementing oil wells the casing isleft within the cemented zone; accordingly, the expense of the apparatusin the cemented zone is an important economic factor for the operator toconsider, especially where zones of extensive depth are to be cemented.However, as the cementing about the casing in a well hole is a criticaland important part of the oil well completion proceeding it must be welland reliably done. While conventional methods and apparatus presently donot perform this operation with entirely satisfactory economy andreliability, according to the process and apparatus of this invention acementing operation is performed with exceptionally good and reliableresults and the apparatus therefor is inexpensively yet reliably made.

It is, therefore, one object of this invention to pro vide an improvedprocess for cementing oil wells.

Yet another object of this invention is to provide an improved apparatusfor the cementing of oil wells.

Still other objects will be apparent to those skilled in the art from astudy of the below disclosure, of which disclosure the drawings attachedhereto form a part and wherein;

FIGURE 1 is a diagrammatic overall view of the apparatus used in aprocess of this invention;

FIGURE 2 is a cross-sectional view along the plane indicated by 2A-2B ofFIGURE 1.

Generally, the process of this invention is directed to cementing of awell bore as 31 Within which is to be located a string 33 of casing ortubing. The string extends from the surface, 35 through a surface earthzone 37, various earth strata as 39, 40, 41, water layers as 43, and gasproducing zones as 45, to the producing zone 47. The casing string iscomposed of surface pipe 49 and a production string generally shown as51. The string 51 is composed of a series of lengths of easing as 53,54, joined in sequence by intermediate collars, as 57, and provided witha shoe, as float shoe 59 at its bottom. In the preferred embodiment thebore of the well 31 below the surface zone 37 is 7% inches in outsidediameter and the casing string 51 is made of 5 /2 inch outside diametersteel casing of a normal weight (e.g. 14 to 17 pounds per linear footwith coupling).

The process of this invention comprises firmly locating and attaching onthe outside of each length, as 53 and 54, of the string 33 in the zoneor length thereof, as 56, throughout which cementing is desired ahot-rolled steel rod, as 61 and 62, in the form of a pre-formed spiral.In the preferred embodiment with a 5 /2 inch outside diameter casing therods 61 are of inch outside diameter and have a pitch of 26 inches andthe spiral is a left-hand spiral. The spiral firmly fits and contactsthe casing and is attached thereto at each 180 of the spiral by a weldof3 inches length between the spiral and the casing. The spiral rod thushas an outer diameter of 6% inches which is substantially greater thanthe standard 6.05 inch outside diameter of the standard collar, as 57,for such casing or tubing, while being substantially less than'theinternal diameter of the well hole, which is 7% inches in the preferredembodiment.

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On each length of easing or piping, as 53 and 54, a length of spiralrod, as 61 and 62 respectively, extends, in the preferred embodimentfrom about 30 inches from the lower end of the length to about 42 inchesfrom the top of that length of easing or piping. This leaves a lowerspace 65 on the bottom end of length 53 (and 65' on length 54) and anupper space 67 on the top end of lengths 53 (and space 67 on length 54).These spaces on the surface of the casing, as 53, are available forattachment thereto of other tools such as centralizers and attachment ofslips and elevators.

The spirals are attached to each length of casing prior to assembling ofthe string. The attachment of the spirals to the tubing is of suflicientstrength so that the spirals cannot be pulled olf the pipe; when atension strength test is applied to them the pipe is pulled in twobefore the spiral is separated from the pipe. The spirals are pre-formedto fit the pipe and provide no mechanical stress for deformation of thatpipe but actually serve to strengthen it; thespirals do not interferewith the pipes elasticity because of the location of the points of theattachment of said spirals with said pipes. The pipe lengths with thespirals thereon as above described are assembled and run to the bottomof the well 31 with a bottom float or guide shoe 59 at the bottom ofsaid string. The well is then circulated to clean it. The tubing string33 is reciprocated with a 10-foot stroke at a frequency of two cyclesper minute prior to putting the cement into the casing. Thisreciprocation is of sufiicient length to cover the length of wellsurface opposite spaces as 65, 67, 65' and 67' not covered by thespirals 61 on the usual 28 to 32 foot length of pipe as 53, 54 used onstrings as 33. The well may be again circulated with mud and/ or waterto clean it out.

The casing is then located vertically in the formation to be cemented,the bottom plug is introduced in the casing, a conventional rotary head71 provided with supports 73 is rotatably connected to string 33 androtatably connects a source of cement 75 to the string 33. A slowsetting cement, below described, is mixed and passed under pressure tofeed pipe 77. A rotary table 79 supporting string 33 is driven by aconventional controllable driving means 81. The cement slurry isinitially at 600 pounds per sq. in. pressure at the surface. Therotation applied by table 79 to string 33 is a right-hand rotation asshown by the arrow 83. More particularly, the left-hand spiral of rodsas 61 provides a counter-clockwise (as seen from above) or left-handspiral on traveling downwards along the edge of such spiral; thedirection of rotation impressed by the table 79 is, as shown by thearrow 83, as seen from above, clockwise.

Conventionally, and according to this process, it takes about 45 to 60minutes between the time the addition of cement to the casing string 33and hole 31 begins and the time when substantially all the cement is inplace, as usually indicated by bumping of the top plug usually added atthe top of the to-be-added cement. According to the process of thisinvention the rotation of string 33 is continued while the cement isbeing moved to its intended position and is continued until the cementstifiens; a 300 HP. motor is used as a drive for a 3,000 foot string:there is a usual draw of 15 to 20 HP. as the cement stifiens the drawrises to 50 HP. In the exemplary em bodiment of this invention, for a3,000 foot hole from 4 to 7 barrels per minute of a mixture, composed of37 pounds Pozmix A Cement (product of Halliburton Oil Well CementingCompany) having an analysis as in Table I below and described in PozmixCement Information, October, 1954, by Chemical Research Laboratory ofHalliburton Oil Well Cementing Company, Duncan, Oklahoma) with 47 poundstype A (A.P.I.) Portland cement, and 1.86 pounds of gel and 17 pounds ofsalt per sack of dry mix, is admixed with 5.75 gallons of water per sackfor a slurry weight of 14.15 pounds per gallon or 1.26 cubic feet persack. This provides a thickening time (as measured by Stanolind highpressure thickening time tester) of about 4 hours and 17 minutes.

The time of thickening is chosen so that there will be a sufficientlylong time after the conventional cement top plug bumps or otherwiseindicating that the cement is in place, for the kneading and otheractions of the rotating spiral rods, as 61 and 62', on each of thecasing lengths as 53, 54 of the string 33 in the to-be-cemented zone, as56, to take place before the cement sets. The cement characteristics arealso chosen, notwithstanding such relatively slow setting, to reduce thetime of waiting for the cement to set to a sufficiently short period tonot economically interfere with any subsequent operations to beperformed on the set cement.

TABLE I Properties of Pozmix A Physical properties:

Specific gravity 2.46 Weight per cubic foot absolute pounds 153.00

Weight equivalent in absolute volume to 1 sack (94 lbs.) cement do 74.00Amount retained on 200 mesh sieve percent.- 5.27 Amount retained on 325mesh sieve do 11.74 Chemical analysis:

Silicon dioxide percent 43.20 Iron and aluminum oxides do 42.96 Calciumoxide do 5.92 Magnesium oxide do 1.03 Sulphur trioxide do 1.70 Carbondioxide do. 0.03 Loss on ignition do 2.98 Undetermined do 2.21

According to this process the cement contacted by the rotating spiralsis densified as demonstrated by that the same volume of cement requiredby normal cementing procedures using conventional cementing proceduresas in Oil Well Cementing Principles and Practices, 1959, B. J. Service,Long Beach, California, page 9) to fill a 650 foot height of annulusbetween 5 /2 inch outside diameter casing and a 7% inch diameter hole,by the process of this invention will fill only from 525 to 570 feet ofsuch annulus. Also, a cement log of a 3,100 foot deep well cemented to atotal height of 2,550 feet with spirals according to this invention forthe bottom 200 feet of such well showed excellent impermeability for theentire 200 foot zone-i.e., from 3,100 foot depth to 2,900 footdepththroughout the depth whereat the spirals extended. Although thesame cement was used and the same period of setting was provided for,not as good cement was provided up to 2,750 feet and the cementingresults were only erratic from 2,750 feet to 2,550 feet of depth.

It is a desirable feature of this invention that the spirals as 61attached to the casing sections as 53 are preformed reliably andeconomically. The tail end of each spiral may be cut off or the tail endmay be turned in toward the axis ofthe spiral and tacked down to thepipe as 53. The lengths of such spirals as needed to cover the length ofthe casing (less inches at one end and 42 inches at the other end) arebutted to each other as at 213 to form a continuous length of spiralalong the usual approximately 30 feet length of each casing as 53.

In the embodiment of the precess above described, with 200 feet of 5 /2inch outside diameter casing working in a 7% inch internal diameter holeto knead 200 feet of cement in the annulus as above described, thefifteen horsepower enregy output of the drive engine as 81 is absorbedsubstantially entirely in the kneading of the thereon.

cement in the vicinity of the spiral as 61 because less than onehorsepower is required to rotate the same string in the same cement at50 to 60 r.p.m. when no spirals are This energy absorption provides ameasure of the energy of kneading. As above described, this energy risesto about three times such total energy input before the rotation of thecasing and the kneading of the cement is usually stopped according tothis process.

In the preferred embodiment a 26" pitch on a 5 /2" outside diametercasing (a pitch of 56 degrees to the horizontal) provides about 8'4" ofspiral for each 10 length of feed ro'd. This pitch is found mostpreferable for providing a sufficient downward component of the kneadingwhile providing a suflicient upward component for permitting andencouraging escape of air and gases from the kneaded cement.

By the apparatus and process herein a complete cement layer is providedaround casing pipe, and slurry and cement are kept uniformly mixed priorto setting. Further, there is also obtained by this process andapparatus a strong bonding between the cement and the pipe due at leastin part to the reentrant angle between the bottom edge of the spiral as61 and the outer surface of the pipe casing as 53. There is also aminimizing of any shrinkage effect due to this kneading action and a lowpermeability in the set product. Furthermore, the pressures otherwiseusually needed for high turbulent flow to provide a good mixing of thecement in the annulus as 215 which might rupture a weak formation areavoided according to thisprocess.- Also according to this process andapparatus of this invention the turbulence of slurry obtained duringcement setting is obtained for the full length of the desired cementingzone as determined by the length of the spiral and is not limited to thevicinity of the casing shoe alone, and, according to this invention,such spirals are sufiiciently inexpensive and reliably made that theymay be applied over the very extensive'length of well hole to becemented. Further according to the process and apparatus of thisinvention air and gases which are drawn into the pipe during thecementing operation or gas which enters the cement as by contaminationfrom well hole liquids and gases is reliably released; thereby thisprocess avoids channeling due to gas absorption below the surface aswell as from gas absorption at the relatively low surface temperaturesand release of that gas at the higher sub-surface and cement settingtemperatures.

While not limiting my invention to the explanation hereinbelow thefollowing is given to set out what I currently believe to be the theoryof operation of the device as provided by the structure apparatusoperation hereinabove recited. The substantial improvement in thecementing product appears due to a tamping and trowelling action. Thisaction is obtained notwithstanding the limited volume available betweenthe outer diameter of the tubing and the inner diameter of the well hole(e.g. only 0.17 cubic feet per linear foot between a 5 /2 inch O.D.casing and a 7% inch I.D. hole). The pressure exerted on the concretebeing set and used as a cementing material in annulus 215 is due to thata substantial proportion of the very high weight of the casingabout50,000 pounds in a conventional 5 /2 inch seventeen pound tubingbears onthe spirals when they rotate.

Because these spirals are firmly attached to the casing the weight ofthe casing is transmitted through those spirals to the cement. This veryheavy pressure and motion of the spirals kneads the cement and therebyexpresses therefrom the air which otherwise causes channeling on settingof said cement. For the purpose of accomplishing this kneading actionwhich removes the air the spirals should be sufiiciently firmly attachedto the casing and rigid, as herein, to bear the weight of the casing inorder to transfer such weight to the cement. The fastening of the spiralto the casing according to this invention does not interfere with thestrength of the tubing. As above described the strength of attachment ofthe spirals to the tubing is as great as the strength of the tubingitself. Accordingly, there is provided an apparatus to accomplish thisforceful kneading. This transfer of pressure through the tubing which isconventionally worked very close to its limit of strength isaccomplished in such a mannerinasmuch as the spirals are preformedthatthere is not additional mechanical strain put on the tubing.

As shown in FIGURE 1 the surface pipe 49 is provided with a right handspiral 50 thereabout. This also made of inch rod as above described andfirmly attached each 180 to the pipe by a 3 inch weld, as 219. Thisright hand spiral 50 serves to draw the section downward through theearth on right hand rotation and facilitate its location. Such righthand spirals are readily made by the'apparatus and process abovedescribed and are readily attached to surface string pipe welding as at221, 222, 223 as described herein for attachment of the tubing 61 to theproduction string pipe length 51.

The composition of cement 66 in annulus 215 is controlled by use ofconventional retarders, such as starch, borox, and sugar to permitkneading until all the gases in the cement slurry are kneaded orotherwise expressed from that slurry. In an exemplary and preferredembodirnent above described a 200 foot length of 5% inch outsidediameter tubing with spirals thereabout in a 7%; inch internal diameterhole draws horsepower when the height of fresh cement slurry, as 66, asshown in FIG. 1, is as high as the top of the highest spiral, as 62, onthe string during the kneading operation. This corresponds to an energyinput rate of about 0.45 horsepower per cubic foot of annulus. Asubstantial rate of energy input, such as horsepower per cubic foot ofannulus appears required to effect an energy of kneading adequate toexpress the air from fresh cement slurry under the conditions of a twoto three thousand foot depth of well. The duration of such energy inputshould be about two hours with a minimum rate of energy input ofone-quarter horsepower per cubic foot. The rate of about .45 horsepowerper cubic foot of annulus is applied for about one hour at the end ofwhich the viscosity of the cement slurry is doubled over its initialviscosity.

The pitch of the spiral 61 is about degrees for the 5% inch outsidediameter pipe 53 with the spiral 61 thereabout as above described. Sucha pitch is adequate to provide effective kneading and also sufficientlysloped to permit the rapid escape of gas which has been expressed fromthe cement by such kneading.

Although, in accordance with the provision of the patent statutes,particular preferred embodiments of this invention have been describedin detail and the principles of the invention have been described in thebest mode in which it is now contemplated applying such principles, itwill be understood that the constructions shown and described are merelyillustrative and that the invention is not limited thereto and,accordingly, alterations and modifications which readily suggestthemselves to persons skilled in the art without departing from the truespirit of the disclosure, hereinabove are intended to be included in thescope of the annexed claims.

I claim:

1. In a process for cementing a well comprising a string of well casingin a well hole in a gas producing formation, the improvement whichcomprises placing a cementitious liquid mixture between the casingstring and the well hole and continuously kneading the cementitiousliquid mixture after it is in place in the space between the casing andthe well hole prior to the setting of said mixture by rotating saidcasing and transmitting weight of the casing by kneading means attachedto said casing, to each portion of said cementitious liquid mixtureimmediately adjacent the casing and moving the said portions of kneadedcementitious liquid mixture from adjacent said kneading means in anunobstructed path outward from said casing toward said wall and backinward to said casing, releasing gas from said cementitious liquid andpassing all said released gas upward in said space, and the saidkneading is performed by a series of solid rigid laterally extendingimperforate spiral extensions, firmly attached to a portion of said wellcasing and said spiral extensions each extending laterally of the easingwith a pitch that is at the same angle to the axis of the Well casing,whereby the kneading action is similar throughout said liquid duringsaid rotation and the rotation of said extensions in said cementitiousliquid prior to its setting is in the direction in which all saidextensions present a similarly downwardly facing imperforate surface,and said extensions reach less than the full distance from the outsidesurface of the casing to the internal diameter of the well hole.

2. Process as in claim 1 wherein the kneading is continued until thecementitious liquid has thickened to at least twice its initialviscosity and the pressure differential to which the cementitious liquidis subjected during such rotation is between 33 and 67 p.s.i., acrosssaid kneading means.

3. Process as in claim 1 wherein the extensions each operate over alength of well casing that is continuous through the major portion ofeach length of well casing forming said string of well casing, and theattachment of said elements to said casing bears a major portion of theweight of said casing string during said rotation of said casing andsaid extensions.

4. Process as in claim 1 where the energy input rate is no less than AH.P. per cubic foot of annulus.

5. Process as in claim 4 where the kneading is accomplished with anenergy input rate of about /2 H.P. per cubic foot of annulus whereby azone of maximum temperature and pressure difierential is createdadjacent said extensions, and said cementitious liquid in said annulusis continuously circulated through said zone prior to its setting.

6. Apparatus for oil well cementing in a well hole comprising, incombination, a string of oil well casing lengths in said well hole, saidstring comprising a series of lengths of imperforate casing joined byexpanded joints of greater outer diameter than the diameter of saidcasing lengths, space between said casing and said hole, preformedrigid, solid spiral rods, each having, as seen from above, acounterclockwise downward path of generation and extending morelaterally from said casing than said joints, each said spiral rod beingfirmly attached at spaced apart points to each of a plurality of saidlengths and extending laterally therefrom to a peripheral surfacethereof, there being a space between said well hole and said peripheralsurface of said solid spiral rods, and means at the surface connected tosaid string for rotating said string opposite to the direction ofrotation of the downward path of generation of said spiral.

7. An apparatus for oil well cementing in a well hole comprising, incombination, a string of imperforate oil well pipe lengths in said wellhole, said string comprising a series of lengths of pipe joined insequence by intermediate collars, said collars having a greater outerdiameter than the diameter of said pipe length, preformed rigid, solidspiral rods each having, as seen from above, a counterclockwise downwardpath of generation and the same angle of pitch relative to the length ofeach said pipes, each said spiral rod being firmly attached at spacedapart points to and reinforcing each of a plurality of said imperforatelengths and extending more laterally therefrom than said collars, therebeing a space between the interior of said well hole and each saidspiral rod, said spiral rods each being firmly attached to a pipe lengthat intervals, the strength of the attachment between each of saidlengths and each of said spiral rods being as great as the strength ofsaid length, means at the surface connected to said string for rotatingsaid string in a direction 7 opposite to the direction of rotation.ofthe downward path of generation of said spiral, and means for addingcement into said string and into said space between said string and saidhole during rotation of said string.

References Cited by the Examiner UNITED STATES PATENTS 220,572 10/79Burgess 166-242 X 1,355,368 10/20 Underwood 29-193 1,358,938 11/20Danglemeyer 153-67 1,460,632 7/23 Wigle et a1 166-241 1,807,050 5/31Stolz 166-21 1,959,367 5/34 Kennedye 308-4 1,959,368 5/34 Kennedye166-21 2,191,189 2/40 Wade 29-193 2,284,969 6/42 Adkinson 166-21 X2,325,462 7/43 Arthur 153-67 2,675,082 4/54 Hall 166-21 l/59 Gist166-173 4/63 Tyrrell 166-241 X OTHER REFERENCES Mills: Rotating WhileCementing Proves Economical, The Oil Weekly, December 4, 1939, pages 14and 15 relied upon.

Composite Catalog of Oil Field and Pipe Line Equipment, 21st Edition,(1955-56), volume 2, Gulf Publishing Company, Houston, Texas, pages 3642and 3643.

Uren: Petroleum Production Engineering (Development) Fourth Edition,1956, McGraW-Hill Book Company, Inc. page 388.

Holt et al.: Rod Welded to Casing Helps Cementing, World Oil, July 1964,pages 97 and 98.

CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN HERSH, Examiner.

1. IN A PROCESS FOR CEMENTING A WELL COMPRISING A STRING OF WELL CASINGIN A WELL HOLE IN A GAS PRODUCING FORMATION, THE IMPROVEMENT WHICHCOMPRISES PLACING A CEMENTITIOUS LIQUID MIXTURE BETWEEN THE CASINGSTRING AND THE WELL HOLE AND CONTINUOUSLY KNEADING THE CEMENTITIOUSLIQUID MIXTURE AFTER IT IS IN PLACE IN THE SPACE BETWEEN THE CASING ANDTHE WELL HOLE PRIOR TO THE SETTING OF SAID MIXTURE BY ROTATING SAIDCASING AND TRANSMITTING WEIGHT OF THE CASING BY KNEADING MEANS ATTACHEDTO SAID CASING, TO EACH PORTION OF SAID CEMENTITIOUS LIQUID MIXTUREIMMEDIATELY ADJACENT THE CASING AND MOVING THE SAID PORTIONS OF KNEADEDEMENTITIOUS LIQUID MIXTURE FROM ADJACENT KNEADING MEANS IN ANUNOBSTRUCTED PATH OUTWARD FROM SAID CASING TOWARD SAID WALL AND BACKINWARD TO SAID CASING, RELEASING GAS FROM SAID CEMENTITIOUS LIQUID ANDPASSING ALL SAID RELEASED GAS UPWARD IN SAID SPACE, AND THE SAIDKNEADING IS PERFORMED BY A SERIES OF SOLID RIGID LATERALLY EXTENDINGIMPERFORATE SPIRAL EXTENSIONS, FIRMLY ATTACHED TO A PORTION OF SAID WELLCASING AND SAID SPIRAL EXTENSIONS EACH EXTENDING LATERALLY OF THE CASINGWITH A PITCH THAT IS AT THE SAME ANGLE TO THE AXIS OF THE WELL CASIN,WHEREBY THE KNEADING ACTION IS SIMILAR THROUGHOUT SAID LIQUID DURINGSAID ROTATION AND THE ROTATION OF SAID EXTENSIONS IN SAID CEMENTITIOUSLIQUID PRIOR TO ITS SETTING IS IN THE DIRECTION IN WHICH ALL SAIDEXTENSIONS PRESENT A SIMILARLY DOWNWARDLY FACING IMPERFORATE SURFACE,AND SAID EXTENSIONS REACH LESS THAN THE FULL DISTANCE FROM THE OUTSIDESURFACE OF THE CASING TO THE INTERNAL DIAMETER OF THE WELL HOLE. 6.APPARATUS FOR OIL WELL CEMENTING IN A WELL HOLE COMPRISING, INCOMBINATION, A STRING OF OIL WELL CASING LENGTHS IN SAID WELL HOLE, SAIDSTRING COMPRISING A SERIES OF LENGTHS OF IMPERFORATE CASING JOINED BYEXPANDED JOINTS OF GREATER OUTER DIAMETER THAN THE DIAMETER OF SAIDCASING LENGTHS, SPACE BETWEEN SAID CASING AND SAID HOLE, PREFORMEDRIGID, SOLID SPIRAL RODS, EACH HAVING, AS SEEN FROM ABOVE, ACOUNTERCLOCKWISE DOWNWARD PATH OF GENERATION AND EXTENDING MORELATERALLY FROM SAID CASING THAN SAID JOINTS, EACH SAID SPIRAL ROD BEINGFIRMLY ATTACHED AT SPACED APART POINTS TO EACH OF THE PLURALITY OF SAIDLENGTHS AND EXTENDING LATERALLY THEREFROM TO A PERIPHERAL SURFACETHEREOF, THERE BEING A SPACE BETWEEN SAID WELL HOLE AND SAID PERIPHERALSURFACE OF SAID SOLID SPIRAL RODS, AND MEANS AT THE SURFACE CONNECTED TOSAID STRING FOR ROTATING SAID STRING OPPOSITE TO THE DIRECTION OFROTATION OF THE DOWNWARD PATH OF GENERATION OF SAID SPIRAL.